Flexible elastomeric articles and reinforcement therefor



March 29, 1966 w. 1.. JACKSON 3,243,338

FLEXIBLE ELASTOMERIC ARTICLES AND REINFORCEMENT THEREFOR Filed Aug. '7, 1961 vdisposed and arranged along the core.

United States Patent O 3,243,338 FLEXIBLE ELASTOMERIC ARTICLES AND REINFORCEMENT THEREFOR William Lewis Jackson, Whitworth, near Rochdale, England, assignor to Dunlop Tire and Rubber Corporation, Buffalo, N.Y., a corporation of New York Filed Aug. 7, 1961, Ser. No. 129,903

7 Claims. (Cl. 16158) This invention relates to flexible elastomeric articles having improved reinforcement and to a pneumatic tire having an improved breaker strip.

According to the invention flexible elastomeri-c articles have embedded therein textile cords which comprise cords of filaments helically wrapped with yarn.

The invention also includes a textile reinforcement having a sheet of parallel cords which comprise filaments helically wrapped with yarn.

The yarn wrapping of the cords which surrounds the inner filaments, also referred to herein as the core of the cord, confers fatigue resistant properties on the cord and on the flexible elastomeric articles wherein the cord is embedded, and increases the stiffness conferred by the filaments.

In applications where stiffness is required in the reinforcement, as in the breaker strips of pneumatic tires for motor road vehicles, this is enhanced by increasing the size of the core and of the filaments which make up the cord, by arranging the filaments so that the cord is substantially circular in cross-section, by minimizing the twist of the filaments and increasing the binding effect of the wrapping, forinstance .by.increasing the tension in the wrapping yarn and by increasing the number of the wrapping yarns, preferably by providing two super posed layers of wrapping yarns which are symmetrically The filaments used in the core may be bonded together by an adhesive.

For use 'as. a breaker strip the' stilfness conferred by using cords as described is suflicient to resist lateral distortion of the tread.

Lateral distortion occurs at the region of contact between the road and the tire when the vehicle to which the tire is fitted is cornering. This distortion causes an ex- ,tensionat one side of the tread and a corresponding compression at the other side. It has been confirmed by experiment that for maximum stiffness and stability the resistance to compression should be substantially equated with the resistance to extension and while steel cords possess these characteristics they are not inherent in textile materials.

3,243,338 Patented Mar. 29, 1966 ice yarns of about 1,650 denier each; more core yarns may be employed if desired but two should preferably not be used since they give a flat cord with increased liability to buckling under compression.

The stiffer man made filaments, such as rayon having 20 denier filaments, are liable to breakage in use and synthetic filaments having greater resilience and less extensibility usually give increased fatigue resistance. Synthetic filaments for use in a breaker strip having two sheets of cords preferably have an extensibility of not greater than 1 percent under a load of 10 lbs. Reduction of stiffness in use is caused at least in part by the cords being forced into an undulating configuration when the breaker strip is deflected with stretching and breakage of the filaments at the turning points of the undulations. Increasing the diameter of the cordsusually increases the fatigue resistance since the wave length of the undulations is increased with a consequent reduction in the points at which the filaments are weakened.

Preferably, the core is wrapped with two layers of wrapper yarns, one wrapped in S direction and the other in Z direction, both having a twist greater than 12 turns per inch and a suitable weight being 840 denier.

In general the degree of twist of the wrapper yarns about the core should be suflicient to ensure that the angle between the wrapper yarns and the longitudinal axis of the cord is greater than 40 degrees. A higher degree of wrapper'twist is required for thin cords than for thicker cords.

The cord may be produced by passing the filaments of the core through a hollow spindle on which a package of wrapper yarn is mounted and wrapping the yarn from the revolving package by means of a ring and traveller as the core is progressed through the spindle. A twist in the core of 2 turns per inch was found suflicient to control the passage of the filaments through the spindle.

The cords may be embedded in the tire carcass or in a separate breaker strip preparatory to inclusion in a tire carcass during molding thereof. It is convenient to employ the cords in the form of a wovenreinforcement sheet having a number of parallel cords which are held in the sheet by transverse binder threads. The sheet is preferably dipped in an adhesive bath, for instance latex,

Theresistance of filaments to compression and conse-' quent buckling increases as the fourth powerof the filament thickness, other things being equal, and the resistance to compression is closely allied to the increase in stiffness in the reinforcement according to the invention. v

,A breaker strip maybe constructed from a sheet of parallel cordsof above about 3,500 denier comprising a core having as low a' twist as is consistent with satisfactory processing, for instance 1 to 3 turns per inch, formed of filaments having a weight per unit length greater than about 6 denier per filament, each cord having a breaking strength of more than about 30 pounds, i.e., a tenacity of more than about 3 grams per denier. The filaments mayconveniently be employed .in three core and 'dried before use and the filaments, or bundles of filaments may be similarly treated prior to wrapping.

The invention willibe further described with reference to the accompanying drawings in which:

helically comprising two sheets of parallel cords.

The textile cord 1 of FIG. 1 has a core of seven symmetrically bunched 840 denier nylon filaments 2. The filaments have a twist of 2 turns per inch and the core a twist of 0.5 turn per inch. The core was wrapped with two wrapper yarns 3, 4 of mixed 300 denier rayon and 210 denier nylon at an angle of 75 degrees with respect to the longitudinal axis of the cord.

The textile cords 1 were assembled in side by side relationship in sheets and dipped in latex. Strips of sheet 5, 6 shown in FIG. 2 were cut and the strips 5 and 6 I were adhered together so as to form a breaker strip with 3 opposed directions symmetrically with respect to the longitud'inal axis of the strips.

The breaker strip was incorporated in a pneumatic tire 7 as shown in FIG. 3.

Cords having the following construction were prepared 4 Breaker strips having sheets with 16 cords per inch were incorporated in tires and the cornering force at 4 degrees slip was obtained before and after running the tires for 500 miles. The extensibility of the cord is given in the 5 followin tab h from filaments having the ply/denier values noted and the fi g e i mdel 21,10 physical properties of the cords were evaluated. The folgums arefgwen S owmg t e 0a 'extenslon ratlos o t e lowing results were obtained. breaker SHIPS- T able I Core Strength Diameter- Cord Core twist, Wrapper in tension (in) Denier t.p.i. (1b.)

Steel* 155 v 0.038 24, 000 3/1650 rayon having 2.3 denier filaments. 35 0. 034 5, 500 3/1650 rayon having denier filaments 0.044 11, 000 30 0. 065 19, 900 7/1650 rayon 70 0. 065 23, 000 l/3,200 teryle 1.0Z 1100 rayon 44 0. 053 14, 500 3/3,200 terylen 1.0Z. 2/840 nylon. 120 1/3,200 terylen 1.0Z- 2 /600 rayon. 44 0. 0386 7, 160 .60 1.0Z. 4/600 rayon 44 O. 0480 11,990 7/840 nylon. 0. 5Z- 2/m ixed: 300 rayon, 210 nylon- 105 0. 0496 10, 330 do 0.5Z 4/mixed: 300 rayon, 210 nylon 105 0. 0592 15, 560 denier filaments- 9S/9Z -2/840 nylon 0.0510 12, 380

*Included for purposes of comparison.

Sheets of parallel cords of the respective constructions noted in Table I were embedded in rubber breaker strips, 30 T able 3 a pair of sheets being provided in each face of the strips 7 which were half an inch thick. The cords of thepairs Load Cornering of sheets were inclined at +20 .and 20 respectively to Cord of ggs; g Tire fififgp force, the length of the strip and the cord density in the sheets Table 1 bility, breaker size bmke,

. .flf' l was 80 percent of the number of cords wh1ch could be F P Sm? g fig included. The stiffness of the breaker strip was determined by measuring the deflection of a three inch wide 0 0 40 465 440 Section of the strip under a load of 150 lb. The following 1 0. 0. 75 b 370 b 370 results were noted. M p 12 0.73 e 294 0294 Table 2 2. 2 1.1 u 260 e 200 7.5 7.5 220 Properties of sheets of cord in sample face *Included for purposes of comparison.

. This cord was made up as cord 10, the nylon of the core being sub- Cord Stiffness jected to hot stretching.

of strip Strength Gord b Proportional cornering force estimated from sheets having 13 cords per inch density 0 per inch. width (11).) (ends Proportional cornering force estimated irom tire treads and breaker in tension per in. strips which were '50 percent wider than those of the other t res.

/ d This tire had four casing plies having cords biassed at some 36", the other tires having two ply casings of heavier cords disposed at 16 3,200 21 .4 800 23 6 1, '600 2 x 23 50 10 540 1s 16 360 12 ig gg Havmg now described my invention, What I claim is: 10 1. In a flexible elastom'eric article, a reinforcement $32 f comprising a sheet of parallel cords, each of said cords 2117 1,680 16 55 comprising a plurality of rigid filaments forming a core 1,470 14 and having a twist of less than 3 turns per inch and a denier greater than 6, and at least two layers of yarns Two pairs of sheets were included in each face of the strip.

Breaker strips having sheets of steel cord 1 and wrapped textile cords 3 of Tables 1 and 2 and conventional breaker strips having a stiffness of 3containing a standard tire cord were incorporated in tires and cornering forceslip angle curves obtained. The curves for the respective tires showed maximum difference at a slip angle of 2 de- 200/:1.43 are in substantial agreement with the cube root of the stifiness ratio.

tightly wound bve'r said filaments and extending at an acute angle with respect to the transverse axis of said cord.

2. The articleof claim 1 wherein said cords each have a denier greater than 3500 and a breaking strength of at least 30 pounds. I

3. The articleof claim 1 wherein adjacent layers of yarns are wrapped in S direction and Z direction respectively.

4. The article of claim 1 wherein the filaments are of nylon and the yarns are of a mixture of nylon and rayon.

' said cords are adhered togetherwith-thei-r cords being 5 6 inclined in opposed directions symmetrically with respect 2,755,214 7/1956 Lyons et al 15452 t0 the longitudinal axis of the reinforcement. 2,782,830 2/ 1957 Wallace 153355 2,786,507 3/1957 Howe et a1. 152--355 References Cited by the Examiner 2,974,559 3/ 1961 Coggi 161-176 UNITED STATES PATENTS 5 FOREIGN PATENTS 271,548 1/1893 TrOtt et a1 174-122 1 21 1 12 1959 France 1,462,453 7/1923 Lerch 152361 2,087,303 Rosch 6t 31 ALEXANDER WYMAN, Primary Examiner. 2,468,304 4 949 Musselrnan 161-17 2 49 359 2 1950 Lessig 152 355 10 EARL BERGERT Emmme 2,598,033 5/1952 Bourdon 57144 L. T. PIRKEY, G. D. MORRIS, Assistant Examiners. 

1. IN A FLEXIBLE ELASTOMERIC ARTICLE, A REINFORCEMENT COMPRISING A SHEET OF PARALLEL CORDS, EACH OF SAID CORDS COMPRISING A PLURALITY OF RIGID FILAMENTS FORMING A CORE AND HAVING A TWIST OF LESS THAN 3 TURNS PER INCH AND A DENIER GREATER THAN 6, AND AT LEAST TWO LAYERS OF YARNS TIGHTLY WOUND OVER SAID FILAMENTS AND EXTENDING AT AN ACUTE ANGLE WITH RESPECT TO THE TRANSVERSE AXIS OF SAID CORD.
 6. THE ARTICLE OF CLAIM 1 WHEREIN THERE ARE AT LEAST TWO SHEETS OF PARALLEL CORDS.
 7. THE ARTICLE OF CLAIM 6 WHEREIN ADJACENT SHEETS OF SAID CORDS ARE ADHERED TOGETHER WITH THEIR CORDS BEING INCLINED IN OPPOSED DIRECTIONS SYMMETRICALLY WITH RESPECT TO THE LONGITUDINAL AXIS OF THE REINFORCEMENT. 